Catalyst components for the polymerization of olefins

Abstract

Prepolymerized catalyst component for the polymerization of olefins CH.sub.2CHR, wherein R is hydrogen or a C.sub.1-C.sub.12 hydrocarbyl group, comprising a solid catalyst component characterized by comprising Mg, Ti halogen and an electron donor (ID) selected from the alkyl esters of aromatic dicarboxylic acids in such an amount that the molar ratio ID/Mg ranges from 0.025 to 0.07 and the Mg/Ti molar ratio is higher than 13, said prepolymerized catalyst component containing an amount of ethylene pre-polymer up to 50 g per g of said solid catalyst component.

Claims

1. A prepolymerized catalyst component for the polymerization of olefins comprising: (i) a solid catalyst component comprising Mg, Ti, and halogen atoms and an electron donor (ID) selected from C.sub.1-C.sub.6 linear or branched alkyl esters of aromatic dicarboxylic acids in such an amount that the ID/Mg molar ratio ranges from 0.035 to 0.043 and the Mg/Ti molar ratio is from 15.8 to 30, and (ii) an ethylene polymer, wherein the prepolymerized catalyst component contains from 0.5 to 3 grams of ethylene polymer per gram of the solid catalyst component, and has an apparent density ranging from 0.35 to 0.39 g/cm.sup.3.

2. A catalyst system for the polymerization of olefins CH.sub.2CHR, in which R is hydrogen or a hydrocarbyl radical with 1-12 carbon atoms, comprising the product of the reaction between: (i) the prepolymerized solid catalyst component according to claim 1; and (ii) tri-n-octyl aluminum.

3. A process comprising polymerizing olefins, CH.sub.2CHR, wherein R is hydrogen or a C.sub.1-C.sub.12 hydrocarbyl group, carried out in the presence of the catalyst system of claim 2.

4. The catalyst system of claim 2, further comprising an external electron donor compound selected from the group consisting of methylcyclohexyldimethoxysilane, diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, (2-ethylpiperidinyl)t-butyldimethoxysilane, (3,3,3-trifluoro-n-propyl)(2-ethylpiperidinyl)dimethoxysilane and methyl(3,3,3-trifluoro-n-propyl)dimethoxysilane.

Description

EXAMPLES

Example 1

(1) Preparation of the Solid Catalyst Component

(2) An initial amount of microspheroidal MgCl.sub.2.2.8C.sub.2H.sub.5OH was prepared according to the method described in ex.2 of WO98/44009 but operating on larger scale and setting the stirring conditions so as to obtain an adduct having an average particle size of 25 m. Into a 500 ml four-necked round flask, purged with nitrogen, 250 ml of TiCl.sub.4 were introduced at 0 C., while stirring, 15 g of microspheroidal adduct prepared as described above. The flask was heated to 40 C. and diisobutylphthalate (DIBP) was added in an amount such as the DIBP/Mg ratio was 0.111. The temperature was raised to 100 C. and maintained for two hours, then the stirring was discontinued, the solid product was allowed to settle and the supernatant liquid was siphoned off.

(3) Then the treatment with TiCl.sub.4 was repeated two more times, omitting the use of DIBP, at a temperature of 120 C. The solid obtained was washed six times with anhydrous hexane (6100 ml) at 60 C. and then dried under vacuum: The characteristics of the catalyst components and the results of the propylene polymerization test procedure are reported in table 1.

(4) Preparation of the Pre-polymerized Catalyst

(5) Into a 60 liters stainless steel reactor, 35 liters of hexane at temperature of 20 C. and, whilst stirring at about 80 rpm, 1500 g of the spherical catalyst prepared as described above, were introduced. Keeping constant the internal temperature, 24 g of tri-n-octyl aluminum (TNOA) in hexane were (slowly) introduced at room temperature into the reactor. Then ethylene was carefully introduced into the reactor at the same temperature, with a constant flow for 18 h. The polymerization was discontinued when a theoretical conversion of 1 g of polymer per g of catalyst was deemed to be reached. After 3 hexane washing at T=20 C. (50 g/l), the resulting pre-polymerized catalyst was dried and analyzed. It contained 1.3 g of polyethylene per g of solid catalyst and its apparent density was 0.390 g/cm.sup.3.

Comparison Example 1

(6) The same procedure described in example 1 was carried out with the difference that a higher amount of DIBP was used bringing to a ID/Mg molar ratio of 0.15. The characteristics of the final catalyst are shown in Table 1.

Comparison Example 2

(7) A prepolymerized catalyst was prepared according to example 1 of WO99/48929. The characteristics of the final catalyst are shown in Table 1.

(8) Gas-Phase Propylene Polymerization

(9) Polymerization Procedure for the Preparation of Propylene Heterophasic Copolymers

(10) The heterophasic propylene copolymers were produced in a pilot plant set-up comprising two serially connected gas-phase reactors. Polymerization is started by feeding separately in a continuous and constant flow the prepolymerized catalyst component in a propylene flow, the aluminum triethyl (TEAL), dicyclopentyldimethoxysilane (DCPMS) as external donor, hydrogen (used as molecular weight regulator) and the monomers in the amounts and under the conditions reported in table 2.

(11) The polymer particles exiting the second reactor are subjected to a steam treatment to remove the reactive monomers and volatile substances, and then dried.

(12) TABLE-US-00001 TABLE 1 Example 1 Comp. 1 Comp. 2 DIBP/Mg 0.043 0.073 0.044 Mg/Ti 15.8 12 12 Apparent density 0.390 0.285 0.292 g/cm.sup.3 % wt Residual after 2 8 5 unloading

(13) TABLE-US-00002 TABLE 2 Example No. 1 Comp. 1 Comp. 2 1.sup.st 2.sup.nd 1.sup.st 2.sup.nd 1.sup.st 2.sup.nd Reactor reactor Reactor Reactor Reactor Reactor T C. 75 70 75 70 75 70 P Barg 24 16 24 16 24 16 Residence time Min 50 22 54 22 54 22 TEAL/DCPMS Wt ratio 8 8 8 TEAL/catalyst (neat) Wt ratio 5 5 5 C3.sup. % mol 94.1 52.7 95.2 53.2 95.6 54.5 H.sub.2/C.sub.3.sup. Mol. Ratio 0.046 0.046 0.046 H.sub.2/C.sub.2.sup. Mol. Ratio 0.13 0.12 0.13 C.sub.2.sup./C.sub.2.sup. + C.sub.3.sup. Mol. Ratio 0.43 0.44 0.43 Split % 81 19 80 20 79 21 Mileage g/g 8600 10600 5900 7300 6500 7930 Xylene solubles Wt %/ 1.7 17 1.6 18 1.8 16 Bulk Density g/cm.sup.3 0.452 0.445 0.444 0.45 0.43 C2.sup. total % 10 10.9 10.7 XSIV 2.7 2.9 3 MFR g/10 13.1 10.2 15 7.6 14.2 8.5